Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F255/00—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00
  • C08F255/02—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00 on to polymers of olefins having two or three carbon atoms
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
  • C08F212/02—Monomers containing only one unsaturated aliphatic radical
  • C08F212/04—Monomers containing only one unsaturated aliphatic radical containing one ring
  • C08F212/14—Monomers containing only one unsaturated aliphatic radical containing one ring substituted by heteroatoms or groups containing heteroatoms
  • C08F212/30—Sulfur
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/04—Acids; Metal salts or ammonium salts thereof
  • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/34—Esters containing nitrogen, e.g. N,N-dimethylaminoethyl (meth)acrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/38—Esters containing sulfur
  • C08F220/382—Esters containing sulfur and containing oxygen, e.g. 2-sulfoethyl (meth)acrylate
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/42—Nitriles
  • C08F220/44—Acrylonitrile
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/52—Amides or imides
  • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
  • C08F220/56—Acrylamide; Methacrylamide
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/52—Amides or imides
  • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
  • C08F220/58—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-(meth)acryloylmorpholine
  • C08F220/585—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-(meth)acryloylmorpholine and containing other heteroatoms, e.g. 2-acrylamido-2-methylpropane sulfonic acid [AMPS]
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/52—Amides or imides
  • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
  • C08F220/60—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing nitrogen in addition to the carbonamido nitrogen
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
  • C08F226/06—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen by a heterocyclic ring containing nitrogen
  • C08F226/10—N-Vinyl-pyrrolidone
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F246/00—Copolymers in which the nature of only the monomers in minority is defined
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof

Definitions

• This invention pertains to superabsorbent crosslinked or graft copolymers formed from an ampholytic ion pair copolymerized with other comonomers.
• the aforesaid crosslinked or graft superabsorbent copolymers are useful for absorbing aqueous electrolyte solutions.
• Polymers for absorbing aqueous electrolyte solutions are used in numerous commercial and industrial applications. For example, polymers are used to improve the water absorbency of paper towels and disposable diapers.
• water absorbing polymers are highly absorbent to deionized water, they are dramatically less absorbent to aqueous electrolyte solutions such as salt water, brine, and urine.
• hydrolyzed crosslinked polyacrylamide absorbs 1,024 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer.
• Crosslinked polyacrylate absorbs 423 grams of deionized water per gram of polymer, but only 10 grams of synthetic urine per gram of polymer.
• Hydrolyzed crosslinked polyacrylonitrile absorbs 352 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer.
• Analogous starch grafted copolymers generally have very poor absorbency to synthetic urine.
• the polymers of the present invention comprise a polymer suitable for use as an absorbent of an aqueous electrolyte solution, said polymer being formed by copolymerization of the following components:
• a further aspect of the invention relates to a method of absorbing an aqueous electrolyte solution comprising the step of contacting the polymers of the present invention with an aqueous electrolyte solution.
• the present invention provides polymers that are highly absorbent to aqueous electrolyte solutions.
• Typical aqueous electrolyte solutions include but are not limited to the group consisting of tap water, salt water, brine, and urine.
• the polymers of the present invention comprise a polymer suitable for use as an absorbent of an aqueous electrolyte solution, said polymer being formed by copolymerization of the following components:
• alkali salts is used generically, unless otherwise indicated, to mean alkali salts including but not limited to salts containing lithium, sodium, potassium, and ammonium cations.
• the term "monomer” is used generically, unless otherwise indicated, to mean monomers, comonomers, termonomers, tetramonomers, etc.
• the term “comonomer” is used generically, unless otherwise indicated, to mean monomers, comonomers, stermonomers, tetramonomers, etc. for polymers wherein there are at least two different monomers.
• polymer is used generically, unless otherwise indicated, to mean homopolymers, copolymers, terpolymers, tetrapolymers, etc., and thus includes polymers prepared using any number of monomers.
• copolymer is used generically to mean polymers prepared using two or more different monomers.
• Graft copolymers as used herein are polymers of one or more species of monomers connected to a main chain as a side chain, exclusive of branch point on the main chain.
• Side chains of a graft copolymer are distinguished from the main polymer chain by the monomer constitution of the side chain i.e., the side chains comprise units derived from at least one species of monomer different from those that supply the units of the main polymer chain.
• the main polymer chain as utilized in the present invention are homopolymeric and copolymeric polymer such as polysaccharide, polypropylene, polyethylene and other polyolefins.
• the side chains are formed of olefinic comonomers and ampholytic ion pairs.
• graft copolymerization is used herein, unless otherwise indicated, to mean a copolymer which results from the formation of an active site or sites at one or more points on the main chain of a polymer molecule other than its end and exposure to at least one other monomer.
• Polymer or copolymer which may be used as main chains in the practice of the present invention include polysaccharides, polypropylene, polyethylene and other polyolefins.
• Polysaccharides suitable for the practice of the present invention include starches, celluloses and glycogens. Common sources of cellulose include but are not limited to cotton, linen, rayon, wood pulp and cellulose xanthine. Currently, cotton gauze is preferred.
• Suitable starches included swollen amylose and amylopectin starches. For the practice of the present invention, these starches should be swollen by heating the starch in water to substantially dissolve the starch granules.
• starches used in the present invention will have less than 30 weight percent amylose based on the weight of the dry starch before graft.
• the preferred starch for use in grafting is soluble starch flour within the range of from about 0 to about 20 weight percent amylose content.
• Polypropylene polymer suitable for use as main polymer chain include polypropylene homopolymers, polypropylene copolymers and polypropylene block-copolymers.
• Polyethylene polymers suitable for use as a main polymer chain include polyethylene homopolymer, polyethylene copolymers and polyethylene block-copolymers.
• the synthetic polymers listed above will be utilized in the form of filaments or thin sheets so that a high surface area to mass will be provided for grafting the comonomers and ampholytic ion pair onto.
• Filaments utilized for grafting will preferably have a denier ranging from about 1 to about 20 denier and most preferably from in the range of about 1 to 8 denier.
• hydrolysis is used generically, unless otherwise indicated, to include hydrolysis of nitrile functionalities and hydrolysis of amide functionalities. These hydrolysis reactions are loosely referred to in the art as “saponification.” Hydrolysis of these functionalities may occur under acidic or basic conditions. Under basic hydrolysis conditions, the term may also include, unless otherwise indicated, neutralization of carboxylic acid and sulfonic acid functionalities.
• the ampholytic ion pair monomer used in the present invention may be prepared by titrating an aqueous solution of a sulfonic acid monomer to pH7 with the amine corresponding to the ammonium cation at a temperature of about 0-15 C.
• the resulting aqueous solution containing the ampholytic ion pair may be purified by contacting the aqueous solution one or more times with small quantities of activated charcoal.
• the concentration of the ampholytic ion pair in the aqueous solution may be determined by evaporatively drying a known amount of the aqueous solution and weighing the residue.
• ampholytic ion pair monomer for use in the preparation of the present invention may be prepared by methods which are well known to those skilled in the art.
• the ampholytic ion pair monomers can be prepared by reacting the amine corresponding to the ammonium cation, e.g., 3-methacrylamidopropyldimethylamine, with the sulfonic acid corresponding to the sulfonate anion, e.g., commercially available 2-acrylamido-2-methylpropane sulfonic acid or 2-methacryloyloxyethane sulfonic acid, in anhydrous tetrahydrofuran. See J.C. Salamone, C.C. Tsai, A.P. Olson, and A.C. Watterson, Adv. Chemical Series , Volume 187, pages 337-346.
• the olefinic comonomers can include but are not limited to the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, 3-methacrylamidopropyldimethylamine, 2-acrylamido-2-methylpropane sulfonic acid, alkali salts of 2-acrylamido-2-methylpropane sulfonic acid, 2-methacryloyloxyethane sulfonic acid, alkali salts of 2-methacryloyloxyethane sulfonic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof. All these suitable olefinic comonomers are believed to be commercially available.
• Suitable crosslinking agents can include but are not limited to the group consisting of N,N-diallylmethacrylamide, diallylamine, N,N-bisacrylamidoacetic acid, N,N'-bisacrylamidoacetic acid methylester, N,N'-methylenebisacrylamide (methylene-bis-acrylamide), N,N-benzylidenebisacrylamide, allylacrylate, diisopropenylbenzene, diallyl succinate, ethylene glycol diacrylate, diallylacrylamide, divinylbenzene, and combinations of two or more thereof. All these suitable crosslinking agents are believed to be commercially available.
• the polymers of the present invention formed from components (a),(b) and (c) were generally prepared by mixing the various monomers in the desired stoichiometric ratios in aqueous solution and then initiating the free-radical copolymerization.
• the polymers of the present invention formed from components (a), (b), and (c') were generally prepared in a two step process, though a single graft copolymerizing step or more than two grafting and polymerizing steps may be advantageously employed.
• the purpose of the two step process is to provide a first grafted polymer wherein the grafted comonomer side chains are more reactive to the polymerization of the ampholytic ion pair monomer.
• Some systems may be reactive enough so that a two step process is not necessary to provide grafted copolymers which are highly absorbent to aqueous electrolyte solutions.
• the multiple step process may be advantageously employed to control the proportions of monomers and relative lengths of the block copolymer chains by graft copolymerizing the various monomers in the desired stoichiometric ratios at the appropriate step of the process.
• the ampholytic ion pair is graft copolymerized onto the polysaccharide or the ampholytic ion pair is polymerized onto the grated comonomer side chains.
• the ampholytic ion pair monomer may be copolymerized with at least one other comonomer.
• the ampholytic ion pair monomer may be copolymerized with at least one comonomer which has a polymerizable olefinic functionality selected from the group consisting of acrylamide (also referred to as AM), methacrylamide, acrylonitrile (also referred to as AN), acrylic acid (also referred to as AA), methacrylic acid, alkali salts of acrylic acid (also referred to as X-AA), alkali salts of methacrylic acid, 3-methacrylamidopropyldimethylamine, 2-acrylamido-2-methylpropane sulfonic acid, alkali salts of 2-acrylamido-2-methylpropane sulfonic acid, 2-methacryloyloxyethane sulfonic acid, alkali salts of 2-methacryloyloxyethane sulfonic acid, N-vinyl-2-pyrrolidone and any
• the polymerization of the ampholytic ion pair may require a higher temperature than the polymerization of some of the other comonomers. Therefore, for the polymerization of the ampholytic ion pair it is desirable to perform the polymerization at temperatures in the range of from about 0°C. to about 90°C. and preferably in the range of from about 40°C. to about 70°C. Those skilled in the art will recognize that the temperatures at which the polymerization is carried out should be varied to allow the various monomers and comonomer to react completely within a reasonable period of time for the method of polymerization utilized.
• graft copolymerization methods for olefinic monomers involve the creation of reactive sites (for example free-radicals) on the main polymer chain. These reactive sites then serve to initiate the copolymerization of the other monomers onto the main copolymer chain.
• Free-radicals reactive sites on the main chain generally are produced by high energy radiation or chemical initiation.
• a common chemical means for creating these free-radicals within polysaccharide polymers and polypropylene polymers is with a chemical oxidation-reduction system.
• oxidation-reduction systems include but are not limited to oxidation-reduction systems selected from the group consisting of ceric ammonium nitrate/nitric acid, ceric ammonium sulfate/sulfuric acid, potassium permasnganate/oxalic acid, hydrogen peroxide/ferrous alkali salts, hydrogen peroxide/ascorbic acid and amine/persulfate.
• Common irradiation means for producing free radicals on the main polymer chain is by utilizing a gamma radiation source (i.e. cobalt 60) or an electron beam.
• the copolymerization of the ampholytic ion pair monomer with the olefinic comonomer and the (c) crosslinking agent or with the olefinic comonomer onto the (c') grafted comonomer side chains can be achieved by any of the well known free-radical polymerization techniques in solution, suspension, or emulsion environment.
• Well known azo compounds commonly employed to initiate free radical polymerization reactions include 2,2'-azobis(N,N'-dimethylisobutyramidine) dihydrochloride, azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2,4-dimethyl(4-methyoxyvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-amidinopropane)dihydrochloride,2-t-butylazo-2-cyano-4-methoxy-4-methylpentane, 2-t-butylazo-2-cyano-4-methylpentane, and 4-t-butylazo-4-cyanovaleric acid.
• Well known inorganic peroxide compounds commonly employed to initiate free radical polymerization reactions include hydrogen peroxide, alkali metal persulfates, alkali metal perborates, alkali metal perphosphates, and alkali metal percarbonates.
• Well known organic peroxide compounds commonly employed to initiate free radical polymerization reactions include lauryl peroxide, 2,5-dimethyl-2,5-bis(2-ethylhexanylperoxy)hexane, t-butylperoxypivilate, t-butylperoctoate, p-menthane hydroperoxide, and benzoylperoxide.
• the compound t-butylhyponitrite is a well known alkyl hyponitrite commonly employed to initiate free radical polymerization reactions.
• ultraviolet light is commonly employed to initiate free radical polymerization reactions with olefinic monomers.
• such other methods of copolymerization as would have occurred to one skilled in the art may be employed, and the present invention is not limited to the particular method of preparing the polymer set out herein.
• the appropriate conditions under which the polymerization reactions described above may be carried out are well known in the art.
• the graft copolymers of the present invention can also be crosslinked with the crosslinking agent (c) described above.
• the crosslinking agent should be admixed with the monomer or comonomers when the side chains, are being formed from the main polymer chain.
• the amount of crosslinking agent admixed with the monomers or comonomers will be in the range of from about 0.01 to about 0.2 weight percent of total weight of monomers and comonomers in the graft copolymerization reaction.
• copolymers of the invention containing an olefinic comonomer with amide, nitrile, carboxylic acid, or sulfonic acid functionalities or crosslinking agent with amide, nitrile, carboxylic acid, or sulfonic acid functionalities can optionally be at least partially hydrolyzed and/or neutralized by heating with aqueous base such as aqueous sodium hydroxide or aqueous potassium hydroxide.
• the degree of hydrolysis and/or neutralization can be controlled by stoichiometrically limiting the amount of base relative to the amount of amide, nitrile, carboxylic acid, and sulfonic acid functionalities. If the hydrolysis is carried out under acidic conditions, the amide and nitrile functionalities can be converted to carboxylic acid functionalities without neutralizing the carboxylic acid or sulfonic acid functionalities of the polymer.
• compositions of the inventive crosslinked ammonium/sulfonate copolymers formed from components (a), (b) and (c) is an effective amount of each of the ampholytic ion pair monomer, olefinic comonomer, and crosslinking agent to produce a polymer highly absorbent to aqueous electrolyte solutions.
• the preferred ranges for the compositions of the inventive polymers given in Tables I-IX reflect the relative stoichiometric amount in mole percent based on the total number of moles of all the various monomers mixed together before the copolymerization.
• the ratio of the crosslinking agent to the other monomers is based on the total number of moles of the ampholytic ion pair and the comonomers.
• the actual composition of the polymers of the present invention produced by the copolymerization reaction may vary slightly from the stoichiometric mixture before the copolymerization depending on the reaction conditions.
• compositions of the inventive crosslinked MPDMA/sulfonate, MEDMA/sulfonate and MEDEA/sulfonate copolymers are given in Tables I, IV and VII, respectively. These broadly preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Tables XXII-XXVII, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive crosslinked MPDMA/sulfonate MEDMA/sulfonate or MEDEA/sulfonate copolymer.
• compositions of the inventive crosslinked MPDMA/AMPS copolymers are given in Table II. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXII, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive MPDMA/AMPS polymer.
• compositions of the inventive crosslinked MPDMA/MES copolymers are given in Table III. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXIII, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive MPDMA/MES polymer.
• compositions of the inventive crosslinked MEDMA/AMPS copolymers are given in Table V. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXIV, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive MEDMA/AMPS polymer.
• compositions of the inventive crosslinked MEDMA/MES copolymers are given in Table VI. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXV, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive crosslinked MEDMA/MES copolymer.
• compositions of the inventive crosslinked MEDEA/AMPS copolymers are given in Table VIII. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXVI, for those polymer compositions which produce an absorbancy of at least 70 gram of synthetic urine per gram of inventive MEDEA/AMPS polymer.
• compositions of the inventive crosslinked MEDEA/MES copolymers are given in Table IX. These more preferred and most preferred ranges for the compositions of the present invention are based on the experimental data provided in Example V, Table XXVII, for those polymer compositions which produce an absorbency of at least 70 gram of synthetic urine per gram of inventive crosslinked MEDEA/MES copolymer.
• the relative amount of the main polymer chain to the total weight of the comonomer and ampholytic ion pair can be chosen to provide a graft copolymer of variable absorbency.
• the main polymer chain constitutes in the range of from about 1 to about 50 weight percent of the total weight of comonomers, ampholytic ion pair and main polymer chain present and most preferably it is preferred that the amount of main polymer chain be in the range from about 5 to about 30 weight percent.
• the polysaccharide grafted polymers of the present invention should be highly biodegradable because the main chain of the graft copolymer is highly biodegradable.
• a further aspect of the invention relates to a method of absorbing aqueous electrolyte solutions comprising the step of contacting the polymers of the present invention with the aqueous solution.
• Typical aqueous electrolyte solutions include but are not limited to electrolyte solutions selected from the group consisting of tap water, salt water, brine, and urine.
• tap water is defined to have an electrolyte concentration of less than 500 ppm of dissolved electrolytes
• urine is defined to have an electrolyte concentration of from greater than 500 ppm to at most 10,000 ppm of dissolved electrolytes
• salt water is defined to have an electrolyte concentration from greater than 10,000 ppm to at most 34,000 ppm
• brine is defined to have an electrolyte concentration of from greater than 34,000 ppm to the saturation point of the solution.
• control data in Table XVI demonstrates that although known crosslinked polymers are highly absorbent to deionized water, they are dramatically less absorbent to aqueous electrolyte solutions such as salt water and urine.
• Polysaccharide grafted polymers are normally much less absorbent to aqueous liquids.
• the polysaccharide substrate which comprises a large portion of the material, is very poorly absorbent to aqueous liquids of all kinds.
• This control data can be used to show that the polysaccharide grafted ammonium/sulfonate copolymers of the present invention can effectively compete with these known crosslinked polymers and exceed the absorbency of these known crosslinked polymers.
• these known crosslinked polymers have questionable biodegradability.
• Known polymer composition include crosslinked polyacrylamide, partially saponified crosslinked polyacrylamide, crosslinked polyacrylonitrile, partially saponified crosslinked acrylonitrile, crosslinked polyacrylic acid, neutralized crosslinked polyacrylic acid, crosslinked polyacrylate, and polymers thereof with sodium 2-acrylamido-2-methylpropane sulfonate.
• the best of these known polymers absorbs up to about 60 grams of urine per gram of polymer, and most of the known polymers absorb much less than 50 grams of urine per gram of polymer.
• the polymers of the control data were prepared by mixing the monomers in the proportions given in Table XVI in an aqueous solution of deionized water. The monomers were present in about 30-40 weight percent relative to the amount of deionized water.
• the free radical polymerization was initiated with commercially available 2,2'-azobis(N,N'-dimethylisobutyramidine) dihydrochloride. About 0.1 mole percent based on the total moles of the monomers of the azo free-radical initiator was employed.
• the reaction was then degassed by bubbling nitrogen gas through the mixture for 15 minutes. The reaction temperature was maintained between 20-35°C. for 24 hours. The reactions produced transparent or cloudy hard gels of the crosslinked polymers.
• a large volume of deionized water was added to the polymer product and the polymers were allowed to swell for about 24 hours.
• the swelled polymers were dried in a forced convection oven at 150°F. The dried polymers were then mechanically blended to a powder.
• Some of the polymers were hydrolyzed and neutralized with a strong base such as aqueous sodium hydroxide or aqueous potassium hydroxide.
• the degree of hydrolysis or neutralization could be controlled by stoichiometrically limiting the amount of base relative to the amount of amide, nitrile, or carboxylic acid functionalities.
• a suspension of 1 gram of the polymer in about 20 milliliters of 0.5 molar aqueous sodium hydroxide was heated to 95°C. until a light golden-yellow color was obtained.
• the mixture was then transferred to a dialysis bag with a molecular weight cut-off of 12,000-14,000 and dialyzed exhaustively against distilled water until the viscous polymer gel had reached pH 7.
• This viscous polymer gel was then poured into a plastic dish and dried in a forced convection oven at 74°C. The dried polymers were then mechanically blended to a powder.
• the dried polymers were then tested for deionized water absorption and synthetic urine absorption.
• About 1 liter of deionized water or synthetic urine was added to 0.1 to 0.5 gram of the dried polymer and allowed to stand for 24 hours.
• the polymer was then separated from the excess unabsorbed liquid by screening through a 100 mesh per inch stainless steel sieve.
• the absorbency was determined by weighing the isolated polymer containing the absorbed liquid and substracting the weight of the dry polymer. The absorbency was measured in units of grams of liquid per grams of polymer.
• the synthetic urine was prepared by dissolving 0.64 gram CaCl2, 1.14 gram MgSO4 ⁇ 7H2O, 8.20 gram NaCl, and 20.0 gram urea into 1000 gram deionized water.
• Several of the polymers were tested two or three times, and the experimental error was within plus or minus 2-5 percent. This small experimental error was largely caused by gel blocking and minor diffusion problems that prevented the aqueous liquid from contacting with all the
• the control data in Table XVII demonstrates that although commercially available water absorbing materials are highly absorbent to water, they are also dramatically less absorbent to aqueous electrolyte solutions such as salt water and urine.
• the commercially available water absorbing materials tested include poly(co-acrylamide-co-acrylic acid) grafted onto starch, a commercial acrylamide polymer sold under the trademark "Water Grabber” ® ("Water Grabber” is a trademark of F. P. Products, Inc.), "LUVS” diaper absorbent (“LUVS” is a trademark of Procter & Gamble Co.), “Pampers” ® diaper absorbent (“Pampers” is a trademark of Procter & Gamble Co.), and "Favor 960” ® (stockhausen, Inc.).
• the best of these known materials absorb up to about 56 grams of urine per gram of absorbing material, and most of the known polymers absorb much less than 40 grams of urine per gram of absorbing material.
• the homopolymers of the ampholytic ion pair monomers with 0.05 weight percent methylene-bis-acrylamide cross linking agent were tested for absorbency to deionized water and synthetic urine according to the method employed in Example I.
• the absorbency of homopolymers is very poor. See Tables XVIII-XX.
• the absorbency to deionized water is about 10 grams water per gram of homopolymer, and only 23 and 17 gram synthetic urine per gram of homopolymer, respectively.
• the absorbency to deionized water is less than 10 gram water per gram of homopolymer, and only 10 and 20 gram synthetic urine per gram of homopolymer, respectively.
• the absorbency to water is less than 10 gram water per gram of homopolymer, and only 10 and 29 gram synthetic urine per gram of homopolymer, respectively.
• the control data in Table XXI demonstrates that although the known ampholytic ion pair 3-methacrylamidopropyltrimethylammonium 2-acrylamido-2-methylpropane sulfonate (MPTMA/AMPS) copolymerized with acrylamide is highly absorbent to deionized water, it is dramatically less absorbent to aqueous electrolyte solutions such as salt water, brine, and urine. The absorbency to synthetic urine is about the same as for the better of the known polymers and commercial materials.
• the MPTMA/AMPS-acrylamide copolymer also has been grafted onto starch using ceric ion or cobalt-60 irradiation.
• starch grafted copolymers are poorly absorbent to deionized water, and only slightly more absorbent to synthetic urine.
• the better of these known polymers absorbs up to about 56 grams of urine per gram of polymer, but the rest absorb less than 30 grams of urine per gram of polymer.
• the polymers of the present invention formed from components (a), (b) and (c) were prepared according to the method described in Example I, except that the inventive polymers were prepared by mixing the monomers in the proportions given in Tables XXII-XXVII.
• the inventive polymers were tested for absorbency to deionized water and synthetic urine.
• the tested polymers comprise polymers formed by the copolymerization of an effective amount of the components listed in the following tables to produce polymers highly absorbent to aqueous electrolyte solutions.
• inventive polymers in these examples which contain an olefinic comonomer with amide, nitrile, carboxylic acid, or sulfonic acid functionalities or a crosslinking agent with amide, nitrile, carboxylic acid, or sulfonic acid functionalities were hydrolyzed and neutralized with an aqueous base such as aqueous sodium hydroxide or aqueous potassium hydroxide.
• an aqueous base such as aqueous sodium hydroxide or aqueous potassium hydroxide.
• Tables XXII and XXIII demonstrates that these polymers exhibit significantly improved absorbency to aqueous electrolyte solutions such as urine over the absorbency of the known polymers listed in Table XVI, the commercially available materials listed in Table XVII, the crosslinked MPDMA/sulfonate homopolymers listed in Table XVIII, and the analogous crosslinked MPTMA/AMPS-acrylamide copolymers listed in Table XXI.
• the preferred MPDMA/sulfonate polymers of the present invention exceed this absorbency to urine by 25-63 percent (70-91 grams synthetic urine per gram of inventive polymer, Table XXII, compared to 56 grams urine per gram for the best known materials, Tables XVI, XVII, XVIII and XXI) without sacrificing absorbency to deionized water.
• Tables XXIV and XXV demonstrate that these polymers exhibit significantly improved absorbency to aqueous electrolyte solutions such as urine over the absorbency of the known polymers listed in Table XVI, the commercially available materials listed in Table XVII, the crosslinked MEDMA/sulfonate homopolymers listed in Table IXX, and the analogous crosslinked MPTMA/AMPS-acrylamide copolymers listed in Table XXI.
• the preferred MEDMA/sulfonate polymers of the present invention exceed this absorbency to urine by 25-116 percent (70-121 grams synthetic urine per gram of inventive polymer, Table XXIV and Table XXV, compared to 56 grams urine per gram for the best known materials, Tables XVI, XVII, IXX and XXI) without sacrificing absorbency to deionized water.
• Tables XXVI and XXVII demonstrate that these polymers exhibit significantly improved absorbency to aqueous electrolyte solutions such as urine over the absorbency of the known polymers listed in Table XVI, the commercially available materials listed in Table XVII, the crosslinked MEDEA/sulfonate homopolymers listed in Table XX, and the analogous crosslinked MPTMA/AMPS-acrylamide copolymers listed in Table XXI.
• the preferred MEDEA/sulfonate polymers of the present invention exceed this absorbency to urine by 25-107 percent (70-116 grams synthetic urine per gram of inventive polymer, Table XXVI and Table XXVII, compared to 56 grams urine per gram for the best known materials, Tables XVI, XVII, XX, and XXI) without sacrificing absorbency to deionized water.
• polysaccharide grafted copolymers of the present invention formed from components (a), (b) and (c') in Tables XXVIII-XXXIII were generally prepared according to the following two step procedure.
• the mixture was then heated to 60°C., at which point a solution of 0.18 g ceric ammonium nitrate in 1.5 milliliters 1 N nitric acid was added to the mixture. After about 1 minute, a 32 weight percent solution of the ampholytic ion pair monomer dissolved in deionized water was added to the warmed mixture. The particulate monomer and relative mole percent added for each of the tested polysaccharide grafted copolymers is provided in the tables. This new mixture was stirred under nitrogen at 60°C. for another 4 hours.
• the pH of the mixture was adjusted to between pH 4 and pH 5.
• the solid crude polysaccharide grafted copolymer was obtained by evaporating the aqueous solvent in a forced convection oven maintained at 74°C.
• the crude grafted polymer was washed by boiling in dimethylformamide to remove any non-grafted acrylonitrile homopolymer. It was then thoroughly washed with deionized water to remove any water soluble polymer.
• the purified grafted material was finally washed with ethanol and dried in a vacuum oven at 60°C. for 24 hours. The dried polymers were then mechanically blended to a powder.
• the yield of polysaccharide grafted copolymer was typically between 60 and 90 percent based on the total weight of the soluble starch, comonomer, and ampholytic ion pair monomer.
• Some of the inventive polysaccharide grafted copolymers containing an olefinic comonomer with amide, nitrile, carboxylic acid, or sulfonic acid functionalities were hydrolyzed and/or neutralized with an aqueous base such as aqueous sodium hydroxide or aqueous potassium hydroxide.
• the degree of hydrolysis or neutralization could be controlled by stoichiometrically limiting the amount of base relative to the amount of amide, nitrile, or carboxylic acid functionalities. For these examples, a stoichiometric excess of the amount of base was used.
• a suspension of 1 gram of the polymer in about 20 milliliters of 0.5 molar aqueous sodium hydroxide was heated to 95°C. until a light golden-yellow color was obtained.
• the mixture was then transferred to a dialysis bag with a molecular weight cut-off of 12,000-14,000 and dialyzed exhaustively against distilled water until the viscous polymer gel had reached pH 7.
• This viscous polymer gel was then poured into a plastic dish and dried in a forced convection oven at 74°C. The dried polymers were then mechanically blended to a powder.
• the polysaccharide grafted copolymers were tested according to the method employed in Example I.
• the preferred polysaccharide grafted MPDMA/sulfonate copolymers of the present invention exceed this absorbency to urine by 81-116 percent (67-80 grams synthetic urine per gram of inventive polysaccharide grafted MPDMA/sulfonate copolymers, Table XXVIII and Table XXIX, compared to 37 grams urine per gram for the best of the known starch grafted polymers Table XVII, and Table XXI without sacrificing absorbency to deionized water.
• the preferred polysaccharide grafted MPDMA/sulfonate polymers of the present invention generally exceed this absorbency to urine by 20-43 percent (67-80 grams synthetic urine per gram of inventive polysaccharide grafted MPDMA/sulfonate copolymers, Table XXVIII and Table XXIX, compared to 56 grams urine per gram for the best known materials, Table XVI, Table XVII, Table XVIII, and Table XXI) without sacrificing absorbency to deionized water.
• the preferred polysaccharide grafted MEDMA/sulfonate copolymers of the present invention exceed this absorbency to urine by 132-232 percent (49-86 grams synthetic urine per gram of inventive polysaccharide grafted MEDMA/sulfonate copolymers, Table XXX and Table XXXI, compared to 37 grams urine per gram for the best of the known starch grafted polymers Table XVII, Table IXX, and Table XXI) without sacrificing absorbency to deionized water.
• These improved absorbencies translate into large savings in the quantity of grafted polymer required and large savings to the consumer.
• the preferred polysaccharide grafted MECMA/sulfonate polymers of the present invention generally exceed this absorbency to urine by 112-153 percent (64.86 grams synthetic urine per gram of inventive polysaccharide grafted MEDMA/sulfonate copolymers, Table XXX and Table XXXI, compared to 56 grams urine per gram for the best known materials, Table XVI, Table XVII, Table IXX, and Table XXI) without sacrificing absorbency to deionized water.
• the preferred polysaccharide grafted MEDEA/sulfonate copolymers of the present invention exceed this absorbency to urine by 70-110 percent (60-78 grams synthetic urine per gram of inventive polysaccharide grafted MEDEA/sulfonate copolymers, Table XXXII and Table XXXIII, compared to 37 grams urine per gram for the best of the known starch grafted polymers Table XVII, Table XX, and Table XXI) without sacrificing absorbency to deionized water.
• the preferred MEDEA/sulfonate polysaccharide grafted polymers of the present invention generally exceed this absorbency to urine by 12-39 percent (63-78 grams synthetic urine per gram of inventive polysaccharide grafted MEDEA/sulfonate copolymers, Table XXXII and Table XXXIII, compared to 56 grams urine per gram for the best known materials, Table XVI, Table XVII, Table XX, and Table XXI) without sacrificing absorbency to deionized water.
• a MEDEA/AMPS ® cotton graft copolymer of the present invention was prepared according to the following procedure.
• the resultant cotton graft copolymer was then washed with water several times to remove any water soluble components.
• the cotton graft MEDMA/AMPS ® copolymer appeared to be uniformly coated on the gauze.
• the graft copolymer was then air dried at room temperature.
• the cotton graft copolymer retained the soft smooth character of the original cotton gauze.
• About 0.60 grams of the cotton graft copolymer was then tested for water absorbency.
• the cotton graft copolymer had a synthetic urine absorbency of about 33 grams of synthetic urine/ gram of cotton graft copolymer. This compares very favorably to cotton gauze which absorbed only 3.7 grams of synthetic urine/gram of cotton gauze.

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• 1991
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